.box {
  width: 400px;
  height: 300px;
  border: 1px solid #999;
  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;
}

.preBox {
  width: 300px;
  height: 200px;
  border: 1px dashed #eee;
}
